AISI 1045 / C45 Medium Carbon Steel: Properties & Heat Treatment
ASTM A29 / EN 10083-2 · Updated: 2026-05-24
AISI 1045 (C45) is a medium-carbon steel with 0.43-0.50% carbon content, offering higher strength and hardness than mild steels while retaining reasonable machinability. Widely used for shafts, gears, axles, bolts, and studs requiring moderate wear resistance. In the normalized condition, it machines well at 170-210 HB. Through-hardening by quenching in water or oil and tempering yields 28-35 HRC for general engineering use. Induction hardening can produce surface hardness of 55-60 HRC for localized wear resistance without affecting core toughness.
Quick Facts
| Category | Carbon Steel |
| Standard | ASTM A29 / EN 10083-2 |
| Density | 7.85 g/cm³ |
| Yield Strength | 450 MPa (65 ksi) Q&T |
| Tensile Strength | 630 MPa (91 ksi) Q&T |
Global Equivalents & Cross-Reference
| Alternative Standard / Grade | Action |
|---|---|
| EN C45 | Compare |
| DIN 1.0503 | Compare |
| JIS S45C | Compare |
| GB 45 | Compare |
| ISO C45E4 | Compare |
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Frequently Asked Questions
Can C45 steel be welded?
C45 has limited weldability due to its higher carbon content, which increases hardenability and cracking risk in the HAZ. If welding is necessary, preheat to 200-300°C, use low-hydrogen electrodes, maintain interpass temperature, and post-weld stress-relieve at 550-650°C. C45 is generally not recommended for critical welded structures—consider 4140 or 4340 for weldable medium-carbon applications.